1. Field of the Invention
The present invention relates to an ultrathin semiconductor circuit having contact bumps and to a corresponding production method.
2. Description of the Related Art
Semiconductor circuits or semiconductor components are electrically connected to carrier substrates or leadframes by various methods including wire, flip-chip and tape automated bonding methods which represent the most important methods. While in the case of the wire bonding method, the individual connection locations or connection pads on the semiconductor circuit or the semiconductor component are successively connected to the corresponding contact locations on the leadframe by means of fine wires (bonding wires). In the case of the flip-chip and tape automated bonding methods, the contact locations or contact pads on the semiconductor circuits or chips are simultaneously contact-connected to those on the carrier substrate in one operation. Therefore, the two last-mentioned techniques are more interesting in principle to the faster contact-connection. The flip-chip and tape automated bonding techniques are gaining in importance because of the increasing number of connection pads on the semiconductor circuit or the semiconductor component.
While in the case of the wire bonding technique, no further layers have to be applied to the contact pads, which preferably comprise aluminum, on the semiconductor circuit. Since the bonding wires, which comprise gold, can be bonded directly on the aluminum surface, it is necessary, for reliably carrying out the contact-connection according to the flip-chip and tape automated bonding methods, to form so-called contact bumps made of contact-connectable and solderable materials on the contact layer elements or contact pads of the semiconductor circuits.
For flip-chip mounting, solder bumps or contact bumps are generally made of material having a high melting point. This material generally comprises a homogeneous alloy material such as Sn/Pb (95/5), which are soldered with a solder deposit situated on the carrier substrate and likewise comprising a tin-lead alloy at low temperatures. In the case of this technique, a defined distance between semiconductor circuit or chip and carrier substrate can be set during the mounting process.
However, a large number of areas of application now demand the use of so-called ultrathin semiconductor circuits or ultrathin semiconductor components having a thickness of less than 300 micrometers. While semiconductor circuits which are contact-connected according to the wire bonding method have minor problems in this case, the above-described semiconductor circuits with contact bumps exhibit an extremely low yield on account of wafer breakages of the semiconductor wafers. These low yields result from the contact bumps (on the wafer front side) which project up to 90 micrometers and, during a grinding operation (on the wafer rear side), lead to a nonuniform pressure distribution and thus to an increased wafer breakage.
Additionally, for the concluding adhesive bonding of the semiconductor component to a carrier substrate after soldering, the conventional flip-chip methods exhibit an inadequate moisture resistance and adhesion on the molding composition used for a housing.
Therefore, there is a need for an ultrathin semiconductor circuit having contact bumps and a corresponding production method, which circuit has a sufficient resistance to breaking even in the case of thicknesses of less than 300 micrometers.